Chemistry Reference
In-Depth Information
Fig. 28 Multifunctionalized CNTs conjugated with EGF target the cell-surface receptor (EGFR)
Multifunctional CNTs are very attractive for drug delivery applications, sensors,
or in the preparation of composites [
12
,
13
,
92
].
Both covalent and noncovalent strategies have been used in order to conjugate
drugs to CNTs and at the same time to increase biocompatibility and decrease
toxicity. Targeted drug delivery with CNTs involves the conjugation of drugs but
also of targeting and/or imaging agents to the same tube and different strategies
have been carefully designed for this purpose.
The approach of coating CNTs with PEGylated phospholipids (PL-PEG) has
been developed by the Dai group. Using this strategy the targeted delivery of
aromatic drugs such as doxorubicin is possible. The aromatic drugs are loaded
directly onto the nanotube surface via
staking and the functional groups on the
SWCNT coating molecules (PL-PEG) can be conjugated with targeting molecules
such as peptides [
128
,
129
].
In another approach, folic acid as targeting ligand has been linked to a Pt(IV)
prodrug compound and then conjugated to PEGlylated SWCNTs [
130
].
On the other hand, covalently modified CNTs possess the advantage of having
functional groups attached on the nanotubes and therefore problems like molecule
desorption are avoided. Thus, Bhirde et al. have used the chemical modification of
carboxylic groups at the nanotube tips and sidewalls, introduced after strong acid
treatment, to attach anticancer agents such as cisplatin and epidermal growth factor
(EGF) to target specifically squamous cancer [
131
] (Fig.
28
).
An alternative strategy for introducing two different and orthogonal functiona-
lizations to CNTs is to perform 1,3-dipolar cycloaddition on the oxidized tubes.
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